Buggy code:
public class JavaTest extends AbstractJavaSamplerClient implements Serializable { private static final long serialVersionUID = 240L ; private long sleepTime ; public static final long DEFAULT_SLEEP_TIME = 100 ; private static final String SLEEP_NAME = "Sleep_Time" ; private long sleepMask ; public static final long DEFAULT_SLEEP_MASK = 255 ; private static final String DEFAULT_MASK_STRING = "0x" + ( Long . toHexString ( JavaTest . DEFAULT_SLEEP_MASK ) . toUpperCase ( Locale . ENGLISH ) ) ; private static final String MASK_NAME = "Sleep_Mask" ; private String label ; private static final String LABEL_NAME = "Label" ; private String responseMessage ; private static final String RESPONSE_MESSAGE_DEFAULT = "" ; private static final String RESPONSE_MESSAGE_NAME = "ResponseMessage" ; private String responseCode ; private static final String RESPONSE_CODE_DEFAULT = "" ; private static final String RESPONSE_CODE_NAME = "ResponseCode" ; private String samplerData ; private static final String SAMPLER_DATA_DEFAULT = "" ; private static final String SAMPLER_DATA_NAME = "SamplerData" ; private String resultData ; private static final String RESULT_DATA_DEFAULT = "" ; private static final String RESULT_DATA_NAME = "ResultData" ; private boolean success ; private static final String SUCCESS_DEFAULT = "OK" ; private static final String SUCCESS_NAME = "Status" ; public JavaTest ( ) { } private void setupValues ( JavaSamplerContext context ) { } @ Override public void setupTest ( JavaSamplerContext context ) { } @ Override public Arguments getDefaultParameters ( ) { } public SampleResult runTest ( JavaSamplerContext context ) { setupValues ( context ) ; SampleResult results = new SampleResult ( ) ; results . setResponseCode ( responseCode ) ; results . setResponseMessage ( responseMessage ) ; results . setSampleLabel ( label ) ; if ( ( ( samplerData ) != null ) && ( ( samplerData . length ( ) ) > 0 ) ) { results . setSamplerData ( samplerData ) ; } if ( ( ( resultData ) != null ) && ( ( resultData . length ( ) ) > 0 ) ) { <START_BUG> results . setResponseData ( resultData . getBytes ( ) ) ; <END_BUG> results . setDataType ( TEXT ) ; } results . sampleStart ( ) ; long sleep = sleepTime ; if ( ( ( sleepTime ) > 0 ) && ( ( sleepMask ) > 0 ) ) { long start = System . currentTimeMillis ( ) ; sleep = ( sleepTime ) + ( start % ( sleepMask ) ) ; } try { if ( sleep > 0 ) { Thread . sleep ( sleep ) ; } results . setSuccessful ( success ) ; } catch ( InterruptedException e ) { getLogger ( ) . warn ( "JavaTest:<seq2seq4repair_space>interrupted." ) ; results . setSuccessful ( true ) ; } catch ( Exception e ) { getLogger ( ) . error ( "JavaTest:<seq2seq4repair_space>error<seq2seq4repair_space>during<seq2seq4repair_space>sample" , e ) ; results . setSuccessful ( false ) ; } finally { results . sampleEnd ( ) ; } if ( getLogger ( ) . isDebugEnabled ( ) ) { getLogger ( ) . debug ( ( ( ( ( whoAmI ( ) ) + "\trunTest()" ) + "\tTime:\t" ) + ( results . getTime ( ) ) ) ) ; listParameters ( context ) ; } return results ; } @ Override public void teardownTest ( JavaSamplerContext context ) { } private void listParameters ( JavaSamplerContext context ) { } private String whoAmI ( ) { } }

Fix:
results . setResponseData ( resultData , null ) ;